Smaller wafer dimensions and the large number of steps required to fabricate state of the art integrated circuits (on semiconductor wafers) require each process step to meet tight specifications. Current semiconductor manufacturing can be divided into: fabrication, circuit probing, assembly and final testing. The process has become sophisticated because the manufacturing technology has progressed rapidly. For semiconductor manufacturers with multiple plants, the manufacturing process may be distributed across multiple sites to achieve optimum capacity control. The materials or semi-finished products may be transferred between different plants to undergo successive processes. The Manufacture Execution System(MES) will encounter some problems when a lot is transferred between plants. For example, a duplicated split lot ID created in different MES systems will only register as a single unit ID in the Enterprise Resource Application(ERP) System. Also, when the lot ID already exists in the imported MES, the transfer function will fail.
The available MES, e.g. PROMIS or IBM Poseidon, generally sets the lot ID. However, when a lot is split and then transferred to another operation plant, there may be a duplicate split lot ID created by the MES of the respective plants. FIG. 1 is a diagram showing lot splitting and ID creating between two plants. With PROMIS, for example, when a lot with lot ID A12345.1 is divided into two lots in Plant A, the first lot keeps the lot ID as A12345.1 and PROMIS in Plant A 12 generates a lot ID A12345.2 for the second lot. When the first lot with lot ID A12345.1 is transferred to Plant B, Plant B accepts A12345.1 to track the first lot in plant B via intranet 16. However, when the first lot with lot ID A12345.1 is divided into two lots in Plant B, the PROMIS in plant B 14 also generates a lot ID A12345.2 for the split third lot. Now, lot ID A12345.2 exists in both plant A and plant B.
In the condition described above, the ERP system cannot identify the second lot and the third lot which are named as the same lot ID A12345.2 by the MES in Plant A and Plant B, respectively. The ERP system can only track one lot, and the management information of the other lot which is named as the same lot ID will fail to register. Additionally, when the split lot with lot ID A12345.2 in Plant A is transferred to Plant B, MES in Plant B will reject the transfer 16 (rejection indicated in the drawing by an “X” through the lower, or second, transfer 16) because the lot ID A12345.2 has already registered in Plant B. The process is stalled.
Another conventional solution to avoid duplicated lot ID is to create an exclusive ID for every lot in each plant by a central control system. However, for semiconductor manufacturers with multiple plants, when the connection between the central control system and the multiple plants is unstable or even disconnected, the lot ID naming will be delayed or suspended. Therefore, the manufacturing follow-up procedures will also stop because of the missing lot ID. The time delay mentioned above for a semiconductor manufacturer can cause major loss. Creating an exclusive ID in the central control system is still not the best solution because of its lack of flexibility.